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Finding the Fourth Proportional to 78.85, 118.31 and 42.80

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Solution

The fourth proportional to 78.85, 118.31 and 42.80 is: 64.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.85 : 118.31 = 42.80 : x
  2. Step 2: Convert to fraction form
    78.85/118.31 = 42.80/x
  3. Step 3: Cross multiply
    78.85x = 118.31 × 42.80
  4. Step 4: Simplify right side
    78.85x = 5,063.75
  5. Step 5: Solve for x
    x = 5,063.75/78.85
  6. Step 6: Final answer
    x = 64.22

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.